From the NCI: "Interstitial implantation of radioisotopes done through a transperineal technique with either ultrasound or CT guidance is being done in carefully selected patients with T1 or T2A tumors. Short term results in these patients are similar to those for radical prostatectomy or external-beam radiation therapy. One advantage is that the implant is performed as outpatient surgery. The rate of maintenance of sexual potency with interstitial implants has been reported to be 86% to 92%, which compares with rates of 10% to 40% with radical prostatectomy and 40% to 60% with external-beam radiation therapy. However, urinary tract frequency, urgency, and less commonly, urinary retention are seen in most patients but subside with time. Rectal ulceration may also be seen. In 1 series, a 10% 2-year actuarial genitourinary grade 2 complication rate and a 12% risk of rectal ulceration was seen. This risk decreased with increased operator experience and modification of implant technique.

Short Term Side Effects
  Immediately after the implant and when the catheter is removed, some men have burning or pressure during urination due to swelling of the gland from the needle punctures. This lasts only a few days. There may also be soreness and bruising behind the scrotal area where the needles were inserted. After a period of two or three weeks further irritation of the gland develops from the radioactivity and the patient may notice burning on urination, pressure,  frequency and some slight rectal irritation or diarrhea. The radioactive half life of the seeds (Iodine-125 60 days and Palladium-103 for 17days) measures how long it takes until half the radioactivity wears off. So after 4 half lives (8 months for iodine and 2 months for palladium) the seeds should only have 1/16 or 6% of their radioactivity left (1/2 X 1/2 X 1/2 X 1/2) There is a small risk of acute obstruction (requiring continued use of the Foley catheter) after the implant, particularly if the gland was large or the patient had some obstructive problems (slow urination) already. We generally use Decadron at the time of the implant and Flomax afterwards to lower the risk

Long Term Side Effects
 The risk of  urinary problems (frequency or incontinence) is very small, as is the risk of rectal problems. (The risk of a rectal ulcer resulting in a fistula is probably less than 1%, and can be caused by a rectal biopsy after a seed implant.)   The risk of impotence is related to age and is higher if the patient also receives external beam irradiation or hormones.A recent review of complications was as noted (Sem Rad Onc 1993;3:240):

There are other uncertain risks (e.g. migration of the seeds into the bloodstream and into the lung:) Implications of radioactive seed migration to the lungs after prostate brachytherapy. Ankem     Urology 2002 Apr;59(4):555-9

To review the incidence and the impact of pulmonary seed migration after prostate brachytherapy on lung function. Isolated reports of seed migration to the lungs after prostate brachytherapy have been published; however, the clinical consequences of this pulmonary migration have not been adequately evaluated. A total of 83 patients underwent prostate brachytherapy during the study period and 58 patients underwent chest radiography. Seed migration occurred in 21 (36.2%) of 58 patients. Thirty-four (0.71%) of 4755 seeds used migrated to the lungs. Clinical and pulmonary function testing revealed no consistent abnormality attributable to seed migration.

Sample Patient Consent Form RTOG 98-05
RISKS AND DISCOMFORTS

Cancer treatments often have side effects. The treatment used in this program may cause all, some, or none of the side effects listed. In addition, there is always the risk of very uncommon or previously unknown side effects occurring.

Implant: The possibility exists for infection but this should be controlled with antibiotics should infection occur. There will be soreness in the implant area. The implant itself has the possible side effects of temporary fatigue, diarrhea, abdominal cramps, bladder irritation with some bleeding, incontinence and, in some patients, inability to have an erection. There is also a chance of permanent injury to the bladder, urethra, bowel, and other tissues in the pelvis. The side effects related to the bladder,urethra, and bowel may take some months to years to occur. Another small risk is the movement of a radioactive seed to the lungs. Very small  amounts of radiation can reach other people. I should follow the special precautions from my doctor if I'm around small children  and pregnant women.

Transrectal ultrasound: Other than discomfort, there really is not a great risk from the transrectal ultrasound.

CT scan with contrast: An allergic reaction due to the contrast dye could occur but, otherwise, this doesn't carry any serious risk.

Anesthesia: There is the possibility of blood pressure problems, heart rhythm problems, breathing changes, drug reactions, nausea, vomiting, headache, sore throat, heart attack, stroke, or death.

Other: There may be some unknown or unanticipated discomforts or risks in addition to those specified above, as this irradiation technique, although not new, is somewhat different from techniques with permanent implantation in the past. Every precaution will be taken to assure my safety to minimize any discomfort that I may experience.